1. Technical Field
The present invention relates generally to a method for real-time delivery of multimedia information requiring a very high bandwidth path over the Internet. More particularly, the subject invention pertains to an architecture and method which allow a client and a multimedia server to communicate over the Internet using current standard Internet protocols, but with the enhancement of enabling the server to use a high bandwidth shared link to transfer large multimedia files which require such an expensive link in order to ensure real time delivery and display of multimedia information at the client end.
2. Prior Art
In the World Wide Web (WWW) environment, a set of protocols are used to allow a user to locate specific pieces of information (also referred to as web pages) and request their transmission to his workstation and their display on his screen in a window through a web browser.
Every piece of information (web page or file) is uniquely identified by a Universal Resource Locator (URL) which has four main parts:
1) the Internet address of the machine hosting the information (also known as the IP address of that machine), PA0 2) the port where the web server software process can be found (the port number usually defaults to number 80), PA0 3) the name of the directory where the page resides on the machine, and PA0 4) the name and type of the file containing the information. PA0 1) The client device has to dedicate storage space to buffer the received multimedia information before it can start to play it to the user. This space may be significant at times. This also implies that client devices must have large local storage resources in order for them to be able to handle incoming multimedia traffic. Network computers and other low cost communication devices generally do not provide such resources. PA0 2) The fact that multimedia information has to be stored, even temporarily, in the client device poses some real concerns among the copyright owners of this information, who would like to see their material delivered exclusively to those users who cannot physically store it and subsequently have the possibility to reuse or redistribute it in an illegal manner.
A simple protocol is used during communications between the user and the www server as described below. This protocol is often referred to as the Hyper Text Transfer Protocol (HTTP) and runs over the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which are the standard protocols of the Internet. This procedure is described hereinbelow with reference to FIG. 1.
It should be clear from the above that the model of communication used in the Internet and the WWW is that the client and the server use a single full duplex link to exchange data as well as commands and responses necessary to exchange the actual data.
In all cases, the information is transmitted to the client at a data rate which cannot exceed the bandwidth of the full duplex link between the server and the client. Typically this is limited to a range from a few kilobits per second to a few megabits per second. In most cases, clients are not directly connected to web servers over a high bandwidth link but rather communicate across a connection spanning several different links interconnected by interworking gateways of various types such as routers, bridges and switches. Consequently, it is usually impossible to guarantee continuous streaming of data over such a concatenation of links and switches or routers. This turns out to be truly problematic if the data to be streamed demands stringent delay and jitter requirements, which is the case of video and audio streams.
The current solution to this problem is to require the client device to first receive the multimedia information and store it in its local disk, and then play it back to the user from that local storage, thus eliminating the effect of jitter from the network.
This approach has at least two main disadvantages.
U.S. Pat. No. 5,321,542 to Freitas, et al. and U.S. Pat. No. 5,448,759 to Krebs, et al. disclose the concept of using two or more channels to transmit data between two systems. The present invention describes a similar idea but with an architecture and method to implement it in the Internet communication network using current standard Internet and WWW communication protocols which do not normally allow this type of communication between two communicating entities on the Internet.